Of same place



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W. W. DEAN.

A TELEPHONE EXCHANGE SYSTEM. No. 597,058. Patented Ja,n1l,18Q8.

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UNITED STATES n PATENT ErrcE.

W'ILLIABII W'. DEAN, OF ST. LOUIS, MISSOURI, ASSIGNOR 'IO THE BELL rITELEIJIIONE COMPANY OF MISSOURI, OF SAME PLACE.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent N0. 597,053, dated January 11, 1898.

Application filed September Z2, 1897. Serial No. 652,538. (No model.)

To @Zt whom t iii/[ty concern:

Be it known that I, IVILLIAM YV. DEAN, a citizen of the United States, residing at St. Louis, in the State of Missouri, have invented a certain new and useful Improvement in Telephone-Exchange Systems, (Case No. 28,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

My invention relates to telephone-exchange systems in which trunk-lines are employed for connecting switchboards at the same or different exchanges, wherebysubscribers connected at one board may communicate with subscribers connected at other boards.

My invention has for its object the adapta tion of trunlr-line systems for use in connection with automatic means jointly controlled by the subscribers and operators for including callinggenerators in circuit With and disconnecting the same from the bells at the called-subscribers stations.

Telephone-exchange systems employing the automatic means referred to form subject-matter of my applications for United States Letters Patent. For example, in my application filed .August 2, 1897, Serial No. 6413, S32, is shown a telephone system equipped with one of the automatic ringing devices referred to. In systems such as is shown in my aforesaid application the calling-generator is automaticallythrown into circuit With the called-subscribers bell when the connecting-plug completes the connection between the callingand called subscribers. The called subscriber in responding to the signal thus automatically conveyed upon removing his telephone from its hook operates the automatic apparatus at the central oice to remove the generator from line. I have found that for various reasons it is undesirable When the called subscriber is connected at another board to ring his bell automatically through the agency of the cord-connecting apparatus and automatic ringing means at the calling subscribers board. Signaling from the calling-subscribers board is especially objectionable when the trunk-lines extend for many miles between different ex changes.

y If it Were not for my present invention it Would be better practice to employ special cord-connecting apparatus at each exchange or board for use in connecting the subscribers for conversation through trunklines, the special cord-connecting' apparatus being unprovided With the automatic ringing apparatus to obviate the various difculties that would otherwise arise in the different trunkline telephone systems.

By means of my present invention I am enabled to employ cord-connectin g apparatus of a uniform type at the various exchanges or boards, which, While it is adapted for automatic signaling when used to connect subscribers at the saine board, is, through the agency of my invention, equally adapted for connecting subscribers at distant boards or exchanges by means of trunlnlines.

Myinvention consists, generally speaking, in providing means associated With each trunk-line adapted to operate the automatic ringing apparatus to remove the generator from circuit with the trunk-line when the trunk-line is connected With the cord-circuit.

I will explain the preferred embodiment of my invention and one application thereof by reference tothe accompanying drawing, which illustrates two subscribers stations, each con nected With separated exchanges or boards by telephone-lines and a trunk-line extend ing between said boards.

The apparatus illustrated Will be readily understood by those skilled in the art, and I do not therefore deem a detaileddescription thereof to be essential.

The subscriber A is connected with a telephone-exchange B, being connected in multiple thereat with spring jacks located at boards a o. et?. The line-indicating apparatus a3 is operated upon the removal of the telephone-receiver at station A in a manner Well understood by those skilled in the art. The subscriber C is one of a number connected with board D, which may be at the same ex change with the boards ct a 0.2 or at a distant exchange. The line of subscriber C terminates in a spring-jack b. The line-indicator c, corresponding to subscriber C, may be operated by rotating the armature of the grounded generator c normally included in IOC circuit with the signal-bell c2, gravity-hook c3, limb c4, and the long line-spring of the springjaok, which is normally in circuit Wit-h the line-indicator.

I have illustrated an answering-plug d and a connecting-plug e, which are united through a centralized battery f and repeating coils f f in a manner well known. Each plug is provided With a tip and sleeve adapted to make contact with the short and long line springs of each spring-jack, respectively, the tips being telephonically united by a strand g, While the sleeves are likewise united by a Strand g.

The operation of the clearing-out indicators h and 7i and the apparatus forming the saine forms no part of my present invention, and as the operation thereof will be readily understood by those skilled in the art I do not deem a further reference thereto to be essential.

A telephone-key Zis provided to include the operators telephone apparatus in a bridge of the oord-circuit. A trunk-line extends in two limbs t 'i' from the board D to the boards d d a2 in multiple. A retardation-coil 7a, which Will pass currents of lour frequency formed by the calling-generator and which is adapted to obstruct voice-currents, is preferably included in a bridge of the trunk-line. In an outgoing trunk-line the retardationcoil is preferably located at the exchange from which the trunk-line extends. At the board D, I have illustrated an operators telephone-key Z', which is adapted to bridge the operators telephone set Z2 between the limbs of the telephonedine, which terminate in a sleeve and tip of the trunk-line connectingplug m. The tip and sleeve of the plug are adapted to make contact with the short and long line-springs of spring-jack h.

I have illustrated a ringing-key n, which upon the insertion of the plug m is adapted, when actuated, to direct calling-current from the generator n/ through the signal-bell c2. An operators indicator o is included in a grounded conductor o', extending from the thimbles of the trunk-line jacks at the eX- change B.

The details of the particular automatic ringing apparatus that I have here shown are fully explained in my aforesaid application, and I Willonly refer to the parts and their functions in the following description of the operation of the system.

Subscriber A, desiring communication with subscriber C, removes his telephone from its hook and thereby lights the lamp of indicator d3. The operator at the board Where the indicator a3 is located inserts the answeringplug CZ Within the spring-jack of the calling subscriber at her board, and having ascertained that C is the desired subscriber the operator then inserts the connecting-plug e in the trunk-line jack at her board. By this act the grounded battery p is closed through the operators annunciator o at board D. The

generator havingbeen removed, as will be hereinafter explained, the D operator listens in and' ascertai'ns that connection with subscriber C is desired, thereupon signaling said subscriber by operating her ringing-key. As in the system of my aforesaid application the armature of magnet q is attracted when the plug c is inserted in the trunk-line jack, since circuit is completed through the same from the grounded battery p to the grounded terminal of annunciator o, the calling-generator fr of ringing-current being thus connected through magnet s with limb t of the trunkline. Now in the particular trunk-line system here shown in order that the operators may converse it is essential that the ringingcurrent generator be disconnected from the telephonie circuit. To accomplish this, I preferably include the retardation-coil L in a bridge of the trunkline, said retardation-coil` as stated heretofore, being capable of passing currents of loW frequency from the calling-generator While it obstructs the voice-currents. As soon as the connecting-plug e is inserted Within the trunk-line jack a path of low resistance is provided for the generatorcurrent through the coil 7c. This path may be traced from the grounded generator through magnet s, sleeve of plug e, the long spring of the spring-jack engaging the plug, the retardation-coil 7c, the short line-spring of said jack, the tip of the inserted plug, a portion of strand g to the grounded connection g2. The magnet s is thus energized sufiiciently to attractits armature, which thereupon Withdraws the stop carried thereupon from the path of the spring or ringing-switch t, which by its own resiliency breaks contact with the generator contact-anvil fr', the generator thus being completely removed from its connection With the trunk-line.

The grounded bell at each of the subscribers stations connected With the exchange B is of high resistance, so that When subscribers are connected for conversation at said exchange the generator will be automatically included in circuit with the bell, and upon the removal of the called-subscribers receiving-telephone from its hook this high-resistance path Will be replaced by a low-resistance path, which Will cause a sufficient increase of the generator-current to operate the magnet I have herein shown but one type of trunkline; but it Will be obvious to those skilled in the art that my invention may be employed to advantage in connection with other types of trunk-lines.

lVhile I have shown one particular form of automatically-controlled signaling apparatus at one of the exchanges, other types may be employed to perform the same Work. I do not therefore Wish to be limited to the precise apparatus herein shown and described; but.

Having thus described my invention, l claim as new, and desire to secure by Letters Patent, only with the limitations expressed or by laiv implied, the following:

IIO

lZO

l. In a trunk-line telephone system, the combination with two switchboards, of a plurality of subscribers connected with each of said boards, signal-receivers at the subscribers stations, a trunleline extending between the boards, switching apparatus at one of said boards for uniting subscribers for conversation, a calling-generator, means for including the same in circuit with the signal-receiver at a called-subscribefs station connected with the latter board, electromagnetic means for removing said generator, apparatus at the subscribers stations connected with the latter board, each being adapted when its station is the called station to operate the latter, means to remove the callinggenerator from circuit with the signal-bell, and a conductor normally connected with the trunk -line adapted to alter the operative condition of the electromagnetic means and to be connected therewith by the switching apparatus upon the manipulation thereof to connect a subscriber whose telephone-line extends to the latter board with the trunleline extending to the other board, whereby the generatoris disconnected immediately upon the establishment of connection with the trunk-line, substantially as described.

2. ln a trunlnline telephone system, the combination with two switchboards, of a plurality ot subscribers connected with each of said boards, signal-receivers at the subscribers stations, a trunk-line extending between the boards, switching apparatus atone of said boards for uniting subscribers for conversation, a calling-generator, means for including the same in circuit with the signalingreceiver at a called-subscribers station connected with the latter board, an electromagnetic circuit-changing device adapted to remove said generator from circuit with the called-subscribers bell, switches at the subscribers stations connected with the latter board, each switch being adapted when its station is the called. station to operate said electromagnetic circuit-changing device to remove the calling-generator from circuit wi th the bell, and a conductor adapted to change the operative condition of the electromagnetic circuitchanging device, said switching apparatus being adapted to connect said conductor with and disconnect it from said electromagnetic circuit-changing device when manipulated to connect a subscriber at the latter board Wit-l1 the trunlcline and to disconnect said subscriber from said trunk-line, substantially as described.

3. In a trunk-line telephone system, the combination with two boards, of a plurality of subscribers connected with cach board, cordconnecting apparatus at one of said boards for uniting subscribers for conversation, a calling-generator, an electromagnet jointly controlled by the cord-connecting apparatus and the apparatus at each subscribers station connected with the latter board when its station is the called station for including the generator in circuit with and removing it from the signal bell or receiver at the called-subscribers station, a trunk-line between the boards, a terminal switch or jack of the trunk-line adapted for connection with the cord-connecting apparatus, and means jointly controlled by the cord-connecting apparatus and said terminal switch adapted to ei'fect the removal of the genera tor from circuit upon the connection of the terminal switch and cord-circuit, substantially as described.

4. In a trunk-line telephone system, the combination with two switchboards, of a plurality of subscribers connected with each board, cord-connecting apparatus for uniting 'subscribers for conversation at one oi` said boards, signal receivers or bells at each subscribers station of comparatively high resistance, a calling-generator, means at the latter board for connecting said generator in circuit with the signal-bell of a called subscriber, an electromagnet included in the circuit traversed by the calling-current, switches, one at each of the subscribers stations connected at the latter board, each switch being adapted when its station is the called station to furnish a path of low resistance for the generator-current, said eleotroinagnet being adapted when the current is thus increased to remove the generator from circuit with the called-subscribers signal-bell, and a retardation-coil connected With said trunk-line affording a path of low resistance for the signaling-current upon the connection of said trunk-line with the cordconnectin g apparatus, whereby the generator is removed from circuit immediately upon the connection of a cord-connecting apparatus with the trunk-line, said retardation-coil being wound to permit of the passage of the calling-current and to obstruct the high-frequency voice-currents, substantially as described.

5. In a trunk-line telephone system, the combination with two switchboards, of a plurality of subscribers connected with each board, cord-connecting apparatus for uniting subscribers for conversation at one of said boards, signal-receivers at each subscribers station, a calling-generator, a ringing-switch adapted when the cord-connecting apparatus is manipulated to connect subscribers at the latter board for conversation to direct current from said generator to the signal-receiver at the called subscribers station, the circuit traversed by said callin g-current being of high resistance, an Velectromagnet connected in said circuit, switches, one at each of the subscribers stations connected at the latter board, each switch being adapted when its station is the called station to furnish a path of low resistance for the generator-current, said electromagnet being adapted when the current is thus increased to remove the generator from circuit with the called-subscribers signal-receiver, and a path of low resistance which is completed through said generaxce IOO

f tor and eleotroinagnet when the oord-connecting apparatus is united with the trunk-line connected with the latter board, each being; adapted when its station is the ealled station 1o operate the latter, means to remove the calling-generator from circuit with the signalfbell, a switch or jack for the trunk-line, and

means jointly controlled by the switching apparatus and the latter switch adapted to effeet the removal of the generator from eireuit. substantially as described.

In witness whereof I hereunto subscribe in v naine thisilth day of September, A. D. lSDT.

WILLIAM W. DEAN.

Vitnesses:

WM. H. WHITE, 'FREDERICK J. RANLETT. 

